Leakage indicator for evacuated and pressurized watchcases

ABSTRACT

An evacuated or pressurized sealed watchcase comprises a member such as a piston or membrane movable in response to a pressure change in the watchcase, and means for signalling the position of the member so as to enable the detection of leaks.

United States Patent [191 Piquere, deceased et al.

[ Aug. 7, 1973 LEAKAGE INDICATOR FOR EVACUATED AND PRESSURIZED WATCIICASES Inventors: Ervin Piquere, deceased, late of Bassecourt, Switzerland; by Ami Scholler, 3, rue Hugi, Bienne; by

- 4l02 Binni r i gembot hof Switzerland executors I I Filed: Dec. 10,1971

Appl. No.:'206,834

Related US. Application Data Continuation-impart of Ser. No. 42,131, June 1, I970, abandoned.

U.S. cl, 58/908, 58/144, 58/152 F Int. Cl. G04b 37/02 Field of Search 58/88, 90, 90 B,

58/144, 152,152 A, 152 F; 73/l24 [5 6] References Cited UNITED STATES PATENTS 2,854,815 10/ I958 Piquerez 58/90 R 3,052,083 9/1962 Piquerez 58/90 A 3,368,751 235/201 2/1958 Merrill Prjmary Exaniin er--Richard B. Wilkinson Assistant Exaniiner-Edith C. Simmons .lackm'on Attorney-Robert E. Burns et a].

[5 7 ABSTRACT An evacuated or pressurized sealed watchcase comprises a member such as a piston or membrane movable in response to a pressure change in the watchcase, and means for signalling the position of the member so as to enable the detection of leaks.

28 Claims, 15 Drawing Figures PATENTEU RUB 7 I975 SHEET 3 0F 5 LEAKAGE INDICATOR FOR EVACUATED AND PRESSURIZED WATCHCASES This application is a Continuation-In-Part of application Ser. No. 42,131 .now abandoned filed on June I, I970.

This invention relates to control of the fluid pressure in sealed watchcases, notably the control that a certain degree of vacuum exists, but also for the control of high 2 by sealing the-watchcase in an enclosure from which" the air hasbeen exhausted, are known.

During the handling of these vacuum watchcases,

damage can occur of such a nature'that several inspections are necessary to verify the hermetic properties of the case, for example, directly after production of the case, when the'watch is being assembled, and, finally before marketing. These inspections are relatively long and costly and a vacuum watchcase having means which'eriable obviation of the succession of inspections on the seal has not yet been successfully produced. It is an object of the invention toprovide a-watchcase which comprises a member displaceable as a result of a certain pressure'differentialin the watchcase, and associated signalling means which enable simple and reliable detection of leaks.

A main aspect of the invention consists of a watchcase comprising a primary enclosure, a member at least a portion of which isdisplaceable, and a secondary enclosure sealed. off from the primary enclosure by means including said displaceable member. A part of the surface of the member is subjected to the pressure in the primary enclosure, and another part of the surface of the member is subjected to the pressure in the secondary enclosure, the member normally being held in a first position by a pressure differential between the primary and secondary enclosures. When the pressurz in the primary enclosure as a result of a pressure passes a certain value, the member is displaceable to a second position. Means: are provided for signalling whether the member is inv the first or second position, and thus enable verification as. to whether the primary enclosure of the watchcase is perfectly. sea-led, or whether there has. been a leakage.

. In one embodiment, the displaceable member can be adeformablje membrane the deformation of which may be observed to provide a signal. Alternatively, such a membrane could actuate mechanical-signalling means.

The displaceable member. could be a piston: slidable inside a. tube-with. a fluidtight packing, member so that when there is a vacuum, the piston slightly protrudes from the tube but in, the event of a: leak, the piston is caused to move. This II-flil.,Can',,fOI example, beplaced horizontally in the'case, under the dial for-example, in such a way that movement of the piston can be observed through. an opening made in; the dial.

Leak detecting means'canconsist of a manometer arranged inside thecase so'that at a predetermined presrous to air. This tube also contains a slug of liquid which moves inside the tube according to the variation of the pressure exerted on theporous substance. It is understood that the liquid must not be liable toevaporate and must be resistant to extreme changes of temperature. Furthermore, the tube must be shockresistant. v

In a sealed evacuated or pressurized watchcase according to the invention only a single-check for leaks is required at the factory, and no other verification is required apart from observation of the signalling means by the retailer or purchaser, and this can be done at any moment without the need for special equipment.

The accompanying drawings show, by way of example, several specific embodiments of the invention, the main part of the sealed watchcase being omitted for the sake of clarity.

FIGS. land 2 are cross-sectional views showing a first embodiment;

FIGS. 3 and 4 are cross-sectional views of a second embodiment;

FIGS. 5, 6 and 7 are cross-sectional views of third, fourth and fifth embodiments;

FIGS. "8 and 9 are cross-sectional views partially showing a sixth embodiment;

FIG. 10 is a partial cross sectional view of a seventh embodiment;

FIGS. 11 and are cross sections of a further embodiment'in two different positions;

FIGS. 13 and 14 are cross-sections'of two further embodiments; and

FIG. 15 is a cross-sectional view of another embodiment.

In the first embodiment shown in FIGS. 1 and 2 an elastic membrane 1, of Isoprene (Registered Trade Mark) for example, is held by its rim in'a rigid,.transparent perspex dome 2 by means of a locking ring 3 driven into the cylindrical wall of the dome 2. A second metal locking ring 4 is driven into the rim of the perspex dome 2, balancing the force exerted by ring 3 and enabling the whole device to be fitted in a watchcase simply by driving it into an opening on a dial 5. Since the device is completely inside the enclosure to be inspected, the only hermetically sealed connection necessary is for the membrane 1 so that the space 6 between the elastic membrane 1 and the perspex dome 2 is isolated from the interior of the enclosure 7.

Before the enclosure 7 of the watchcase is evacuated, the elastic membrane is in the position shown in FIG. 1. When the enclosure 7 comes under vacuum, the membrane 1 adopts a concave shape as a result of the different pressure usually atmospheric pressure or a selected low pressure, present in thespace 6. In the event of a leak in the watchcase so that the pressure in the enclosure 7 rises to equalor abovethat in the space 6, the membrane 1 changesshape from concave to convex, and this change of 'shape can be observed through the dome 2. y

When the elastic membrane is very small, it is difficult for the human eye to clearly and rapidly distinguish the convex shape of the membrane from the concave shape. FIGS. Sand 4 show an embodiment of the invention, which aims to facilitate distinguishing the confrom the membrane 1. In addition, an aperture 10, the

edges of which more or less meet when the diaphragm 8 is in the rest position, as shown in FIG. 4, is bored in the central part of this diaphragm.

The membrane 1 and the diaphragm 8 are in contrasting colors or, if that is not possible, the central part of the membrane 1 carries on its surface a signalling area 11 of'a material which is in a color contrasting to that of the diaphragm 8.

When the enclosure of the watchcase is not under vacuum, the membrane 1 is convex-shaped, and exerts pressure on the diaphragm 8 which is distended such that the aperture opens and reveals the membrane 1, or the colored area 11, as shown in FIG. 3. When the enclosure is under vacuum, the membrane 1 is concave-shaped and spaced apart from the diaphragm 8, the aperture of which closes thereby concealing the membrane 1.

It is known that when observed through an aperture, an opaque cavity appears black in color. This effect is used in the embodiment of FIGS. 5 and 6 to facilitate observation of the change in shape of a membrane similar to that of FIGS. 1 and 2. The opaque enclosure is formed by an elastic membrane 12, a black screen 13 with a central opening 14, and an interposed packing ring 15. In FIG. 5, this assembly is housed in an inner recess in awatch glass 16, with the membrane 12 hermetically sealed by a ring 17. In the position shown, the enclosure of the watchcase is not under vacuum and the membrane 12 is convex-shaped with its apex sufficiently close to the opening 14 to be visible. This visibility can be facilitated by coating the membrane 12 with a bright or reflecting colored varnish 18. When the watchcase enclosure is evacutated, the membrane '12 bulges inwardlY and is spaced apart from the opening 14 which appears black and blends with the screen 13.

In order not to weaken the glass, or if the latter is made of mineral glass or sapphire, the device may be mounted in an auxiliary glass 19, as shown in FIG. 6.

FIG. 7 shows a mounting of a membrane 12 in a space defined by the membrane 12, the auxiliary glass 19 with an aperture 20, and the glass 21 wherein the space is at atmospheric pressure. Prior to evacuation, or after a leak in the watchcase, the membrane 12, under its own elasticity adopts the position shown, whereas when the main enclosure of the watchcase is under vacuum the membrane 12 bulges inwardly.

It should be noted that in the embodiments of FIGS. 5, 6 and 7, the device is used simultaneously to conceal the center part of the watch dial.

In the embodiment shown in FIGS. 8 and 9, an elastic membrane 12 is also mounted in an opaque enclosure formed by two interfitting cylindrical parts 33 and 34 with an opening 35 in part 34, the whole unit being fixedin a watchcase to the dial.

When the case is not under vacuum, the membrane 12 is concave-shaped and is practically invisible (FIG. 8). On the other hand, when the case is under vacuum, the membrane 12 tends to become convex-shaped and comes into contact with the edge of the opening 35 to produce a shape in which the central part 120 of the membrane bulges through the aperture 35 thereby .becoming clearly visible. Height-wise, this embodiment is particularly small.

FIG. 10 shows an embodiment where the change in shape of an elastic membrane 22 can be observed by the same means as in the embodiment of FIGS. 3 and 4 and also by a mechanically operated cylindrical display device 36 controlled by the membrane 22 which, in this embodiment, is used above all as an actuator.

The elastic membrane 22 is mounted in a perspex dome 23 by means of a metal ring 24 driven into the dome 23, an opaque apertured diaphragm 25 being interposed between the membrane 22 and dome 23. The perspex dome 23 is housed in an opening in a watch dial 26.

The mechanically operated display device 36 consists of a cylinder horizontally pivoted in a recess in the dial andhaving secured thereto a hammer-shaped lever arm 27 whose rounded end is urged against the membrane 22 by the action of a light spring 28 held in position by a screw 29. The cylinder 36 has two rectangular-shaped areas 30 and 31 each of a different color. Observation of these areas is through a rectangular aperture 32 which is of approximately the same width as each of the areas 30 and 31.

In FIG. 10, the device is shown when the enclosure is not under vacuum. The membrane 22 is convexshaped and the area 30 of the cylinder 36 appears under the aperture 32. When the enclosure is under vacuum, the membrane 22 becomes concave-shaped and pushes the arm 27 downwards thereby bringing the area 31 under the aperture 32.

The display using such a cylinder provides for a more precise reading and, in particular, facilitates the observation of a slight increase in the pressure of the enclosure.

In this last embodiment, observation using a diaphragm 25 is clearly not essential, nor is the use of a transparent dome 23.

As a general rule, for the above embodiments, it is not essential to use an elastic hermetically sealed membrane which always has either a convex or a concave dome-like shape, and a membrane or diaphragm of another shape e.g. a flat one, when in a rest position, can also be used especially in conjunction with a mechanically operated display device such as the one shown in FIG. 10, or any mechanical transmission device or mechanical or electrical signalling device which enables movement of the membrane to be observed.

FIG. 11 and 12 show an optical tell-tale device in which the signal is entirely mechanical. This device consists of a tube 41 provided with a thread 42 and a crown 43 by which it can be gripped by a suitable tool to screw it into a wall 44 of the enclosure of a watchcase in which it is required to check the vacuum. A piston 45 is slidably mounted in the tube 41, and has a packing joint 46 which enables the piston to slide in the bore of tube 41, but ensures a sufficient fluidtightness for gas between a space 47 and the inside of the case. Tube .41 isclosed at its outer end by a glass-48 driven into a collar in crown 43 between an interiorbezel ring 49 and a fluidtight packing member 50. Piston 45 is extended by a cylindrical neck 51, the surface. 52 of which is colored, preferably in red.

In the space 47, is a gas at low pressure equal to or greater than the low pressure itis desired to maintain inside the watchcase. When the vacuum is produced in the case, the pressure of gas in space 47 will have the tendency topush the piston inwards. If the initial pressure difference between space 47 and the enclosure is greater than the frictional force of joint 46 it is possible to hold the piston shown in FIG. 11 by a stop.

If the case has a leak, the air penetrating therein increases the pressure in the enclosure. The piston is thus pushed forward into the position shown in FIG. 12, so that the colored surface 52 is visible. This constitutes an alarm signal which can be made more clearly visible by givinga reflective polish to the surface 53 of bezel 49.

The sensitivity of the device can be set by choice of pressure in the space 47.

In the embodiment shown in FIG. 13 a tube 54in which a piston 55 can move is closed by a glass'56 driven into the tube, and a bezel ring 57 into which is screwed an electric bulb 58.

In this example, the piston 55 contains an electric battery 59 held therein by means of a threaded stopper 60, a fluidtightseal being ensured by a packing member 6]. The battery 59 is resiliently held in position by a spring 62. When the piston moves in the direction of the glass 56 as a result of a leakage of air into the watchcase enclosure, a pole 63 of battery 59 comes into contact with a terminal of bulb 58, the circuit being completed through the bulb holding bezel ring described for evacuated cases, the same constructions 'is not a conductor, contact between the piston 55 and the tube 54 can be ensured by a spring blade contact (not shown).

According to another embodiment, illustrated in FIG. 14, a transparent or translucent elastic membrane 65 is attached by its edges between a sapphire glass 66 and a bezel ring 67 having a conical reflecting surface 67a produced by metallization, for example. Glass 66 is attached to the supporting tube, by a crimped edge 68 ensuring the necessary pressure for holding the membrane 65. A piston 69 is made in one piece from synthetic material, for example polyethylene of Teflon (Registered Trademark), and has two circular bosses 69a and 69b acting as piston ringsPiston 69 has an aperture 70 to enable mounting thereof. The device is illustrated in its non vacuum position. After placing the device in a watch, the desired vacuum is produced in the case, which has the effect of pulling the piston 69 could be used as leakage detectors in pressurized watchcases, the only difference beingthe normal position adopted by the membrane. For example, in the embodiment of FIGS. 3 and 4, the membrane would be in ,the FIG. 3 position when the watchcase is pressuriied and would be deformed to the FIG. 4 position in the case of leakage.

What is claimed is:

l. A watchcase comprising a primary enclosure, a member at least a portion of which is displaceable, a secondary enclosure sealed off from the primary enclosure by means including said member, a part of the sur face of said member being subjected to the pressure in said primary enclosure and another part of the surface of said member being subjected to the pressure in said secondary enclosure, said member normally being held in a first position by a pressure differential between said primary and secondary enclosures and being displaceable to a second position when the pressure in said'primary enclosure passes a certain valueas a result of a leak, and means for signalling whether said member is inthe first or second position.

' 2. A watchcase according to claim 1, in which said displaceable member is a deformable membrane.

away from the glass 66 so as to bring it into the position I shown in the drawing, the flexible membrane 65 being deformed so that it takes up the position 65' shown in broken lines. Through the glass 66 an observer will thus see a particular image consisting of Newton's rings formed by reflection and interference. Should air penetrate into the case, the piston will be pushed towards the glass and the curvature of the membrane will decrease which brings about a dimming of the light and then the disappearance of the Newton's rings. The wearer or watch repairer is thus warned that the watch is no longer perfectly sealedv a The embodiment shown in FIG. 15 employs a manometer as the signalling means. A transparentdome 80 is affixed to a dial 82 through an opening in the latterand a manometer capillary tube 84 is mounted within the dome 80 by means of a plug 85. The interior of the tube 84 is evacuated and contains therein a slug of liquid 87. The lower end of the tube 84-is closed by a porous substance 88 wh'ich'is permeable to airbut not to the liquid slug 87. Thus when a leak occurs in the 3. A watchcase according to claim 2, in which said signalling means comprise a part of said membrane visible through a transparency at least partially defining said secondary'enclosure.

4. A watchcase according to claim 2, in which said signalling means comprise an observational aperture through which a part of said membrane is visible in one of the first and second positions of the membrane but invisible in the other of said first and second position of the membrane.

S. A watchcase as claimed in claim 4, in which said aperture is formed in a distensible diaphragm adjacent said membrane, said diaphragm and the aperture being distended by the membrane in said one of the first and second positions of the membrane, and said diaphragm occupying a position in which said aperture is substantially closed when said membrane is in said other of said first and second positions.

6. A watchcase as claimed in claim 4, in which said aperture is formed by a transparent section of an opaque screen adjacent said membrane, a part of said membrane being in the proximity of said aperture in said one of the first and second positions of the membrane, said membrane being spaced apart from said aperture in said other of the first and second positions of the membrane.

7'. A'watchcase as claimed in claim 5, in :which said part of the membrane carries a reflective surface coat-- ing ofa color contrasting to that of the opaquescreen.

8.'A watchcase as claimed in'claim 4,'in which said aperture is formed by an opening in a screen adjacent the membrane, a part of said membrane protruding through the openingin said one of the first and second positions of said membrane, said membrane being spaced apart from said opening in said other of the first and second positions of the membrane.

9. A watchcase as claimed in claim 1, in which said secondary enclosure is formed by an inner recess in a watch glass sealed off from the primary enclosure by means including the membrane.

10. A watchcase as claimed in claim 9, in which said watchcase comprises a second glass fitted outside the first one.

11. A watchcase as claimed in claim 10, in which said secondary enclosure communicates with a space defined between the first and second glasses.

12. A watchcase as claimed in claim 2, in which said signalling means comprise an observational aperture, a signalling member visible through said aperture, and means foractuating the signalling member in response to movement of the membrane.

13. A watchcase as claimed in claim 12,'in which said signalling member is rotatably mounted under said aper't'ure, said actuating means comprising a lever mounted for rotation with the signalling member and means for holding an end of the lever against the membrane so as to follow movement of the membrane. 7

14. A watchcase as claimed in claim 13, in which said signalling member comprises first and second discrete differently colored areas respectively visible through said aperture when the membrane is in the first and second position.

15. A watchcase as claimed in claim 1, in which saidmember is a piston movable in a tube.

16. A watchcase as claimed in claim 15, in which said primary enclosure is under vacuum, and an end of the piston is located in a secondary enclosure sealed off from the primary enclosure and at a given pressure equal to or greater than a pressure desired to be maintained in the primary enclosure.

17. A watchcase as claimed in claim 15, in which a fluidtight packing member is located between the piston and the tube.

18. A watchcase as claimed in claim 15, in which the signalling means comprises a colored part of the piston visible from outside the casing when the piston is in one of the first and second positions.

19. A watchcase as claimed in claim 18, in which the colored part of the piston is located at an end of the piston in the secondary enclosure, said secondary enclosure being defined between the tube, a fluidtight packing member between the piston and the tube, the piston and a transparency covering an end of the tube, said tube being hermetically fitted into a wall of the watchcase.

20. A watchcase as claimed in claim 1, in which the signalling means comprise an electrical signalling member actuated when the member is in the second position.

21. A watchcase as claimed in claim 15, in which said secondary enclosure is defined between the tube, a fluidtight packing member, the piston, and a transparency covering an end of the tube, an electric bulb in the secondary enclosure having one contact connected to the tube and another contact co-operating with power supply means carried by the piston when the piston is in the second position.

22. A watchcase as claimed in claim 15, in which the signalling means comprises a membrane located adjacent a transparency.

23. A watchcase as claimed in claim 22, in which in one of the first and second positions of the piston the signalling means produces Newtons rings.

24. A watchcase as claimed in claim 15, in which the piston is in synthetic material and has at least two annular bosses acting as piston rings and forming fluidtight packing members with the tube.

25. A sealed watchcase having means for detecting a leak, in which said detecting means comprises a manometer tube closed at one end and having a slug of liquid movable along the tube to signal when a leak is present within the watchcase.

26. A sealed watchcase comprising means for detecting a leak, said detection means comprising a piston movable in a tube between a first and a second position, the piston occupying the first position when an enclosure in the case is under vacuum and being movable to the second position upon an increase in the pressure in the enclosure, and means for signalling when the piston is in second position.

27. A sealed watchcase comprising means for detecting a leak, said detection means comprising a transparent cap sealed in a wall of said watchcase and a flexible diaphragm held inside said cap and having its periphery sealed to said cap, said diaphragm being movable in said cap between a first position and a second position and occupying the first position when the enclosure in the case is under vacuum and being movable to the second position upon an increase in the pressure in the enclosure, and means for indicating the position of said diaphragm, said indicating means comprising a portion of said diaphragm which is visible from outside said cap when the diaphragm is in second position.

28. A sealed watchcase according to claim 27, in which said cap is cylindrical with a closed outer end and has an annular shoulder formed in its side wall spaced from said end, and in which a ring pressed in said cap at the inner end clamps the periphery of said diaphragm between said shoulder and said ring. 

1. A watchcase comprising a primary enclosure, a member at least a portion of which is displaceable, a secondary enclosure sealed off from the primary enclosure by means including said member, a part of the surface of said member being subjected to the pressure in said primary enclosure and another part of the surface of said member being subjected to the pressure in said secondary enclosure, said member normally being held in a first position by a pressure differential between said primary and secondary enclosures and being displaceable to a second position when the pressure in said primary enclosure passes a certain value as a result of a leak, and means for signalling whether said member is in the first or second position.
 2. A watchcase according to claim 1, in which said displaceable member is a deformable membrane.
 3. A watchcase according to claim 2, in which said signalling means comprise a part of said membrane visible through a transparency at least partially defining said secondary enclosure.
 4. A watchcase according to claim 2, in which said signalling means comprise an observational aperture through which a part of said membrane is visible in one of the first and second positions of the membrane but invisible in the other of said first and second position of the membrane.
 5. A watchcase as claimed in claim 4, in which said aperture is formed in a distensible diaphragm adjacent said membrane, said diaphragm and the aperture being distended by the membrane in said one of the first and second positioNs of the membrane, and said diaphragm occupying a position in which said aperture is substantially closed when said membrane is in said other of said first and second positions.
 6. A watchcase as claimed in claim 4, in which said aperture is formed by a transparent section of an opaque screen adjacent said membrane, a part of said membrane being in the proximity of said aperture in said one of the first and second positions of the membrane, said membrane being spaced apart from said aperture in said other of the first and second positions of the membrane.
 7. A watchcase as claimed in claim 5, in which said part of the membrane carries a reflective surface coating of a color contrasting to that of the opaque screen.
 8. A watchcase as claimed in claim 4, in which said aperture is formed by an opening in a screen adjacent the membrane, a part of said membrane protruding through the opening in said one of the first and second positions of said membrane, said membrane being spaced apart from said opening in said other of the first and second positions of the membrane.
 9. A watchcase as claimed in claim 1, in which said secondary enclosure is formed by an inner recess in a watch glass sealed off from the primary enclosure by means including the membrane.
 10. A watchcase as claimed in claim 9, in which said watchcase comprises a second glass fitted outside the first one.
 11. A watchcase as claimed in claim 10, in which said secondary enclosure communicates with a space defined between the first and second glasses.
 12. A watchcase as claimed in claim 2, in which said signalling means comprise an observational aperture, a signalling member visible through said aperture, and means for actuating the signalling member in response to movement of the membrane.
 13. A watchcase as claimed in claim 12, in which said signalling member is rotatably mounted under said aperture, said actuating means comprising a lever mounted for rotation with the signalling member and means for holding an end of the lever against the membrane so as to follow movement of the membrane.
 14. A watchcase as claimed in claim 13, in which said signalling member comprises first and second discrete differently colored areas respectively visible through said aperture when the membrane is in the first and second position.
 15. A watchcase as claimed in claim 1, in which said member is a piston movable in a tube.
 16. A watchcase as claimed in claim 15, in which said primary enclosure is under vacuum, and an end of the piston is located in a secondary enclosure sealed off from the primary enclosure and at a given pressure equal to or greater than a pressure desired to be maintained in the primary enclosure.
 17. A watchcase as claimed in claim 15, in which a fluidtight packing member is located between the piston and the tube.
 18. A watchcase as claimed in claim 15, in which the signalling means comprises a colored part of the piston visible from outside the casing when the piston is in one of the first and second positions.
 19. A watchcase as claimed in claim 18, in which the colored part of the piston is located at an end of the piston in the secondary enclosure, said secondary enclosure being defined between the tube, a fluidtight packing member between the piston and the tube, the piston and a transparency covering an end of the tube, said tube being hermetically fitted into a wall of the watchcase.
 20. A watchcase as claimed in claim 1, in which the signalling means comprise an electrical signalling member actuated when the member is in the second position.
 21. A watchcase as claimed in claim 15, in which said secondary enclosure is defined between the tube, a fluidtight packing member, the piston, and a transparency covering an end of the tube, an electric bulb in the secondary enclosure having one contact connected to the tube and another contact co-operating with power supply means carried by the piston when the piston is in the second position.
 22. A watchcase as clAimed in claim 15, in which the signalling means comprises a membrane located adjacent a transparency.
 23. A watchcase as claimed in claim 22, in which in one of the first and second positions of the piston the signalling means produces Newton''s rings.
 24. A watchcase as claimed in claim 15, in which the piston is in synthetic material and has at least two annular bosses acting as piston rings and forming fluidtight packing members with the tube.
 25. A sealed watchcase having means for detecting a leak, in which said detecting means comprises a manometer tube closed at one end and having a slug of liquid movable along the tube to signal when a leak is present within the watchcase.
 26. A sealed watchcase comprising means for detecting a leak, said detection means comprising a piston movable in a tube between a first and a second position, the piston occupying the first position when an enclosure in the case is under vacuum and being movable to the second position upon an increase in the pressure in the enclosure, and means for signalling when the piston is in second position.
 27. A sealed watchcase comprising means for detecting a leak, said detection means comprising a transparent cap sealed in a wall of said watchcase and a flexible diaphragm held inside said cap and having its periphery sealed to said cap, said diaphragm being movable in said cap between a first position and a second position and occupying the first position when the enclosure in the case is under vacuum and being movable to the second position upon an increase in the pressure in the enclosure, and means for indicating the position of said diaphragm, said indicating means comprising a portion of said diaphragm which is visible from outside said cap when the diaphragm is in second position.
 28. A sealed watchcase according to claim 27, in which said cap is cylindrical with a closed outer end and has an annular shoulder formed in its side wall spaced from said end, and in which a ring pressed in said cap at the inner end clamps the periphery of said diaphragm between said shoulder and said ring. 